Dialkylated silicon esters and method of making them



Patented May 25, 1948 DlALKYLATED SILICON ESTERS AND METHOD OF MAKING THEM Rob Roy McGregor, Verona, and Earl Leatlien War-rick, Pittsburgh, Pa., minors to Corning Glass Works, Corning, N. Y., a corporation of New York No Drawing. Application June 6, 1945, Serial No. 597,950

4 Claims.

This invention relates to the alkylation of silicon compounds, particularly the silicon esters such as ethyl orthosilicate --Si(OC2Hs) 4.

This application is a continuation-in-part of our copending application Serial Number 416,-

285 filed October 23, 1941 since matured into U. S. Patent No. 2,380,057, dated July 10, 1945,

authors, Andrianov and Gribanova, describe the preparation of monoalkyltriethoxysilanes by reacting metallic magnesium, alkyl halide and ethyl orthosilicate in the absence of ether. It is stated in this article that while the monoalkyltriethoxysilane can be obtained in fair yields, it is difllcult to obtain dialkyldiethoxysilanes by this method. Specifically, the mono-isopropyl and mono-isoamyltriethoxysilanes were described as being prepared but the corresponding. disubstituted silanes were not obtained.

We have discovered that dialkyldiethoxysilanes can be made in substantial yields by reacting magnesium, alkyl halide and ethyl orthosilicate in the absence of ether provided the alkyl radical of the halide is a normal allryl radical having from 3 to 5 carbon atoms.

An object of this invention is to produce dialkylated silicon esters in a simple and economical manner.

Another object isto alkylate a silicon ester in the absence of ether or other solvent.

To these and other ends the invention comprises reacting a halide of a normal alkyl radical having from 3 to 5 carbon atoms with a mixture of metallic magnesium and ethyl orthosilicate in the absence of ether and other solvents.

We have discovered that ethyl orthosllicate can be dialkylated by means of a nascent magnesium alkyl Grignard reagent in the absence of ether when the alkyl radical of the Grignard reagent is selected from the class consisting of n-propyl, n-butyl, and n-amyl radicals. In other words, disubstitution occurs when the Grignard reagent, instead of being prepared separately in an ether solution before mixing it with ethyl orthosilicate,

salts and other by-products. Hence a 100% yield of the reagent based on the amount of magnesium employed cannot always be expected. The same holds true with our process wherein the Grignard reagent is formed in situ. However, when equimolecular quantities of the alkyl halide, the silicon orthoester and magnesium are used we have obtained products which contain about two-thirds as much of the dialkylated ester as they do of the mono-alkylated ester. Based on the results of our experiments the reaction is believed to roceed according to the following general equation which does not take into account the possible formation of small amounts of the trialkylated ester and complex derivatives:

R is a normal alkyl radical having from three to five carbon atoms and X is a halogen.

The reaction of metallic magnesium with an alkyl chloride does not start as readily as with an alkyl bromide and when the chloride is employed it is usually necessary to initiate the reaction b the addition of a small amount of a starting catalyst such as ethyl bromide preferably in conjunction with iodine after which the reaction with the chloride proceeds readily.

For a better understanding of our invention reference should be had to the following example which is included by way of illustration and not limitation.

Example Two thousand and eighty (2080) grams of ethyl silicate were added to three hundred'and sixty (360) grams of magnesium and thirteen hundred and eighty-seven grams of n-butyl chloride. The resulting mixture was placed in a pressure-tight reaction vessel and stirred. The pressure rose to lbs. in 40 minutes. Stirring was continued for 3% hours. Distillation at atmospheric pressure (760 mm.) of the product yielded 215 grams of liquid boilng between 192 and 193 C., and 595 grams boiling at 220 C. Analysis established the first fraction to be mono-n-butyltriethoxysilane and the second fraction to be di-n-butyldiethoxysilane. Corresponding yields of mcnoand di-n-butylethoxysilanes were likewise obtained when the above reaction was carried out in a vessel equipped with an adequate condenser instead of a pressure-tight vessel.

In a similar manner, di-n-propyl. i a 1 and di-n-amyldiethoxysilane were prepared fr n-propyl chloride and n-amyl chloride, respectively.

The silanes produced by the method set forth in the above examples are useful either to render siliceous surfaces water-repellant or as intermediates in the preparation of siloxane polymers. The latter are produced upon hydrolysis and condensation of the silanes.

We claim: Y

1. The method of making a dialkyldiethoxysilane which comprises reacting an alkyl halide with metallic magnesium and ethyl orthosilicate in the absence of solvent, the allwl substituent of said alkyl halide being selected from the class consisting of'n-propyl, n-butyl and n-amyl radicals, and allowing the reaction to continue until a substantial quantity of the dialkyldiethoxysilane is obtained.

2. The method of making a dialkyldiethoxysilane which comprises reacting an alkyl chloride di-n-butyldiethoxysilane.

4 The method of making di-n-butyldiethoxysilane which comprises reacting n-butyl chloride with metallic magnesium and ethyl orthosilicate with metallic magnesium andethyl orthosilicate' said alkyl halide being selected from the class conin the absence of solvent, the alkyl substituent of in the absence of solvent, fractionally distilling the reaction product, and recovering therefrom di-n-butyldiethoxysilane.

ROB ROY MCGREGOR. EARL LEATHEN WARRICK.

summons crrnn The following references are of record in the me of this patent:

- Andrianov et al.: Jour. Gen. Chem., USSR, 8

a (No. 6). pages 558-82 (1938). 

